diff --git a/tox.ini b/tox.ini
index fa3d57ab1..bcee22487 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,12 +5,16 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
+whitelist_externals = find
 install_command = pip install -U {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands =
+  find . -type f -name "*.pyc" -delete
+  find . -type d -name "__pycache__" -delete
+  python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:pep8]
 commands = flake8